Process of treating artificial threads



Patented Nov. 6, 19 34 UNITED PROCESS OF TREATING ARTIFICIAL CilHREADSThomas F. Banigan, Buffalo, N. Y., assignor to Du Pont Rayon Company,New York, N. Y., a corporation of Delaware No Drawing. ApplicationFebruary 12, 1930, Serial No. 427,962

4 Claims.

This invention relates to a process of treating artificial threads. Moreparticularly, it relates to purifying, such as desulphuring andbleaching, artificial threads produced by the viscose,

1 5" method.

In the manufacture of artificial silk by the viscose method it is thepractice to spin the viscose solution through fine orifices into acoagulating bath and receive the thread on a collection device, such asa bobbin or rapidly rotating bucket. The freshly spun thread is thentreated for the removal of the adhering coagulating bath liquor andsubsequently with a desulphuring solution, whereby the sulphurimpurities produced in the spinning operation are eliminated. The threadis finally washed and dried. If the thread is to be bleached, thisoperation is carried out on skeins of the previously dried thread.

The washing and desulphuring treatments are commonly carried outwhilethe thread is on the bobbin by the drip method wherein water or othersuitable solutions are permitted to drip over the thread, until thedesired result has been effected. Processes have already been proposedfor the ::treatment of the thread on perforated bobbins wherein thewashing and desulphuring operations are effected by pressure or vacuumtreatment. In

such processes the cleansing or purifying liquid is forced through thelayers of the wound thread. In addition to being slow and tedious, noneof 'the drip purifying processes are practical when the spinning iscarried out under considerable tension and wherein a very compact andtightly wound cake of thread is formed on the bobbin. -The pressuremethod of desulphuring artificial thread wound on bobbins, particularlyif the artificial thread has been wound under considerable tension, hasmany serious disadvantages. To obtain good desulphuring it is necessaryto 40 flow a considerable amount of the desulphuring liquid through thecake of artificial thread on the bobbin. Artificial thread wound onbobbins forms an exceedingly effective filter. Thus, unless thedesulphuring liquid is perfectly clean, and this is exceedinglydifficult in actual practice, the ar- 'tificial thread becomescontaminated by the filtering out and depositing on itself of theimpurities suspended in the treating liquid. This danger ofcontamination is true in the case of either .low or high tension spunartificial thread but much more so in the latter case. The treatment ofthe artificial thread tightly wound on bobbins has also been renderedvery difficult by the inability to obtain sufiloient fiow through thecake 554 :to maintain the uniformity of temperature throughout the cakenecessary for uniform desulphuring of all parts of the cake. Inaddition, these processes necessitate the use of comparatively highliquid pressure as, for instance, 15-50 pounds per square inch, and theprovision of equipment for producing and withstanding these pressures.The equipment must therefore be made elaborate and at the same time beconstructed of special materials capable of withstanding the chemicalaction of the desulpuring liquid. The use of pressure or vacuumdesulphuring therefore becomes very costly and uneconornioal.

I have found that I can eliminate the above disadvantages and provide avery effective method of desulphuring artificial thread, particularlythat tightly wound on a bobbin, by the simple process of immersing thethread in a suitable purifying solution for a sufficient time to insurethe complete purification of the thread.

It is therefore an object of this invention to provide a simple processof purifying artificial thread produced by the viscose process and whichconsists in immersing the thread in a purifying solution.

Another object of this invention is to provide a method of desulphuringartificial thread produced by the viscose process which consists inimmersing the thread tightly wound on bobbins in a desulphuring solutionfor a sufficient time to insure a complete removal of the sulphurimpurities.

Additional objects will appear from the following description andappended claims.

According to one mode of practicing this invention, the viscose solutionis spun in the usual manner and, after coagulation and regeneration ofthe cellulose, the freshly spun thread is received on a bobbin. Thethread on the bobbin is then washed with water in any suitable manner toremove the adhering coagulating bath and/or regenerated bath liquors.The thus washed thread, while it is on the bobbin, is immersed in adesulphuring solution and maintained therein for a sufficient length oftime until the desired result is obtained without employing anyadditional operations to induce fiow of said solution through said cake.In treating thread produced in a method of utilizing considerabletension, it is preferable to dry the thread prior to desulphuring andsubsequent to washing. By such treatment the swollen cellulose hydrateis converted into a more compact thread of cellulose and a large numberof voids are provided in the cake. This condition of the thread permitsa more ready penetration of the desulphuring solution. Furthermore,since the cake is dried, the concentradetails of manipulation andtreatment, the intion of the desulphuring solution in contact with thethread is not diluted and the operation is permitted to be moreexpeditiously performed.

Any of the common and well known solutions may be used as a desulphuringsolution. In case aluminum bobbins or other apparatus made of aluminumare employed, it is preferable to use a desulphuring solution comprising0.1% to 0.5% of sodium sulphide and sodium silicate in such proportionsas to produce 0.05% to 0.5% of silica.

The process may be operated at any convenient temperature such as, forinstance, approximately 40 0., although it is clear that the temperatureand/or the concentration of the solution maybe varied to suit differentpurposes.

It is apparent that the method previously described is simple inoperation and. very economical. In addition to desulphuring tightlywound artificial thread without the necessity of incur-V ring theexpense of converting the thread into skeins before treatment, theherein-described method produces a much improved thread. The presence ofsmall amounts of insoluble impurities in the purifying liquid does notaffect the process. Only a small amount of treating liquid enters thecake; hence a comparatively small amount of impurity is introduced and.capable of being deposited on the rayon.

While this invention has been described with particular regard todesulphuring of tightly wound artificial thread on bobbins, it is clearthat the principles of this invention may also be applied in thebleaching process in a similar manner or to any of the purification orfinishing opera- Itions that may be desired. Furthermore, the inventionmay be successfully used in the treatment of threads in the form ofbucket cakes or any other form of freshly spun artificial thread.

Since it is obvious that various modifications and changes may be madein the above specific vention is not restricted thereto except as setforth in the appended claims.

I claim:

1. In a method of producing artificial thread by the Viscose process,the steps of washing a cake of thread, drying said cake, immersing saidcake in a purifying solution and maintaining the cake in said solutionuntil the desired results have been obtained without employing anyadditional operations to induce the flow of said solution through saidcake.

2. In a method of producing artificial thread by the viscose process,the steps which consist in washing a cake of tightly wound thread,drying said cake, immersing said cake in a desulphuring solution andmaintaining the cake in said solution until the desired results havebeen obtained without employing any additional operations to induce theflow of said solution through said cake.

3. In a method of producing artificial thread by the viscose process,the steps of winding freshly produced thread on to a bobbin, subjectingthe thread on the bobbin to a Washingtreatment, drying the thus washedthread, immersing the dried thread and the bobbin on which it is woundin a purifying solution and maintaining the cake in said solution untilthe desired results have been obtained Without employing any additionaloperations to induce the flow of said solution THOMAS F. BANIGAN.

